Hi Mike!
To play the game all you need is the pdx file (or rather the zip file). You should be able to head over to play.date and login to your account, then go to sideload, choose a file and just upload the .zip file (1_4.pdx.zip) and wait for it to finish uploading.
After that you should find it in the play date device, just gotta refresh the list of games and then download it.
Sometimes I think it can glitch out if your updating a game (ie you already have it installed and wanna update). If that happens I would suggest removing it on the device and in your play.date sideload page and just upload it again. Saved data should still remain)